What Hardware is Required
CPU
MockMotor is a multi-threaded application, and can use as many CPUs are you give it.
For a mocked transaction without configured delay, MockMotor uses one CPU per transaction, and the maximum concurrency is defined by the number of available CPUs.
However, since most LT transactions have a configured response time higher than the required CPU time, the thread releases CPU early and MockMotor reaches much higher concurrency on a small number of CPUs.
Ballpark figure: Give it 4 CPUs per expected 100 TPS.
Memory
For performance, MockMotor stores all mock responses in memory, precompiled. That requires a noticeable amount of RAM, sometimes a few GB.
Ballpark figure: Allocate 1M of RAM per reaction.
In a clustered setup, each node stores a copy of each compiled response. All nodes in cluster use the same amount of RAM.